Indian researchers detect spoiled food with LEDs

It’s a significant development in the contact-free monitoring of food

A team of researchers at the Indian Institute of Science Education and Research (IISER) in Pune, India, has developed new LEDs which emit light simultaneously in two different wavelength ranges, for a simpler and more comprehensive way to monitor the freshness of fruit and vegetables. As the team writes in the journal Angewandte Chemie, modifying the LEDs with perovskite materials causes them to emit in both the near-infrared range and the visible range, a significant development in the contact-free monitoring of food.

Professor Angshuman Nag and PhD student Sajid Saikia, explain their idea: “Food contains water, which absorbs the broad near-infrared emission at around 1000 nm. The more water that is present [due to rotting], the greater the absorption of near-infrared radiation, yielding darker contrast in an image taken under near-infrared radiation. This easy, non-invasive imaging process can estimate the water content in different parts of food, assessing its freshness.”

Using these modified phosphor-converted (pc)-LEDs to examine apples or strawberries, the team observed dark spots that were not visible in standard camera images. Illuminating the food with both white and NIR light revealed normal coloring that could be seen by the naked eye, as well as those parts which were starting to rot, but not yet visibly so.

The researchers emphasize that the pc-LEDs are easy to produce without any chemical waste or solvents and short-term costs could be more than recovered by the long service life and scalability of this novel dual-emitting pc-LED device.

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